The present invention relates to a method and apparatus for measuring and recording the isometric muscle strength of many if not all of the major skeletal muscle groups in the human body. More particularly, the present invention relates to a chair apparatus and method of using the same, providing for testing of multiple major skeletal muscle groups at a single test station.
Muscle strength can be defined as the ability of a muscle or group of muscles to produce tension or exert force through the human skeletal system. The muscle may contract in three different ways: (1) concentrically (force is generated while the muscle is shortening in length); (2) eccentrically (force occurs while the muscle is being elongated; and (3) isometrically (force is generated by a muscle whose length is not changing).
The generally accepted measurement criterion for the maximum tension which can be exerted by a muscle is the maximum amount of force a muscle can exert on a body part. This is referred to as the maximum strength of the muscle and might be expressed, for example, in kilograms per square centimeter of transverse section. Strength measurements should be taken at a proportional distance from the axis of rotation of the body part when comparing measurements from different subjects. This is particularly important when the force exerted by the body part is the parameter to be measured. With respect to this methodology, moment measurements should also be taken at a proportional distance from the axis of rotation.
Muscle strength testing devices typically utilize a rotating input shaft. If concentric, eccentric and/or isometric strength is to be measured, an accurate positioning of the axis of rotation of the rotating input shaft of the apparatus taking the measurement with the actual center of rotation of the body segment being assessed is required. Reasonably adequate placement has been achieved by a significant number of currently available muscle strength testing devices for testing the knee. A widely used device for measuring strength and endurance of human muscles is the Cybex II apparatus, which is described in various materials and in U.S. Pat. No. 3,465,592. However, as discussed above, this device requires that the axis of rotation of the rotating input shaft of the apparatus taking the measurement be aligned with the anatomical center of rotation of the body segment being assessed.
A recently issued patent (U.S. Pat. No. 4,462,252) describes a method and apparatus for measuring the strength of the flexors and extensors of the trunk; however, this device measures the muscle strength and endurance for only this one part of the body. This device and other devices are designed to measure concentric and often eccentric strength with the incidental ability to assess isometric strength. The complex and bulky speed control/load cell mechanisms required to test concentric and eccentric strength are difficult, if not impossible, to move from one skeletal muscle group site to another and assure proper alignment therewith so as to enable testing of multiple muscle groups at a single device or testing station.
Additionally, the muscle groups to be tested must be isolated from muscle groups which may contribute a moment of force to the apparatus measuring the muscle groups. Accordingly, the human subject must be positioned appropriately and the parts of the body containing muscles which are not part of the measurement must be stabilized or immobilized.
Prior art devices have typically not been capable of providing adequate stabilization of body parts not being tested and/or of appropriately aligning force measuring components for most if not all of the major muscle groups of the body at a single device or station. In some cases, individual devices may adequately stabilize the subject and align the device for a single or limited number of muscle groups, but these devices are not capable of appropriate stabilization and alignment for most if not all of the major muscle groups of the human body.
The present invention solves these and many other problems associated with prior muscle strength and endurance testing devices.